1. Field of the Invention
The present invention relates to a driving device for advancing an elongated element, such as for instance a cable, a rope, a rod or any other elongated element, rigid or flexible, of any cross section profile.
2. Description of Related Art
It is known how to advance an elongated element in its axial direction by gripping it between two driving means, for example two wheels or two track belts. In the case where the elongated element is rigid, such as for instance a rod, the device can function by pushing or by pulling. In the case where the elongated element is flexible, such as for instance a rope, the device can function only by pulling.
The driving device must be capable of adapting to different elongated objects to transport, notably to the transverse dimension of the object, or to its diameter in the case of a cylindrical object, by adjusting the gap between the contact surfaces of the two driving means and two opposed surface portions of the object to transport.
In the known devices, the gap between the two driving means is adjusted by maintaining the position of one of the driving means and by transversely displacing the other driving means until the gap allows the object to travel between the two driving means. The disadvantage of such a device appears when one wishes for elongated elements of rather different diameters to travel. By keeping one driving device fixed, one has a transverse displacement of the elongated element's longitudinal axis for two elongated elements of different transverse dimensions. This can be a disadvantage in certain situations, notably in the case where the alignment of the axis of the elongated element to transport, relative to the devices which precede or follow the driving device, is important.
Another disadvantage of known devices is that it is generally difficult or sometimes impossible to adjust the set pressure of the two driving devices on the object while permitting the device to absorb an instantaneous variation of the object's transverse dimension, for example during the passage of a splice between two successive lengths of the object.
Yet another disadvantage of known devices is that the gap between the two driving means is adjusted by working successively on several distinct means, such as for instance on regulating screws, which is tedious and can entail a subsequent adjustment of the exact alignment of the driving device, especially in the case of two track belts.
On the other hand, in the case of tracked driving devices, it is sometimes necessary to replace one or the other of the driving track belts, either because of wear or to adapt them to the elongated element to transport. In the known devices, it is necessary to remove at least one of the tension rollers of each belt in order to loosen it so that it can be replaced.